The invention relates to an aerofoil sub-assembly for use in the formation of a hollow aerofoil, particularly an aerofoil for use as a fan blades in a jet engine. The engine also relates to an aerofoil made from the sub-assembly and a method of making such an aerofoil.
Hollow aerofoils are commonly used on fan blades in civilian turbo fan engines. They are also increasingly used on modern military aircraft. The hollow blades are considerably lighter than solid fan blades. Typically, the blade cavity is formed by super plastic forming (SPF) with some form of internal metallic structure to increase strength and stiffness of the blade and to prevent the skin surfaces of the blade “panting” ie oscillating in and out relative to each other.
It is known to introduce a visco-elastic damping material into the hollow cavity to increase damping and reduce vibration.